1832.] of the Doab Canal 455 



time, and with the least possible labor ; at the same time avoiding the 

 application of superstructure in the shape of a fixed road-way and 

 lifting gates; in short, to throw the whole dam as open as possible, 

 and to relieve it from any obstructions that may interfere with the 

 free passage of the floating timber, &c. It will appear evident, that, 

 the best sort of dam in a position of this nature would be a simple 

 flooring of masonry, with flanks of the same material ; the bund 

 or bank for retaining the water being constructed of earth, gabions, 

 &c. which although it would be annually washed away during the 

 rains, would be repaired at a trifling expense, and the space of masonry 

 between the flanks would provide an escape sufficiently ample, and at 

 the same time perfectly free and unimpeded by any interruptions from 

 piers, &c. in its width. This species of dam would best suit a situation, 

 where the heavy freshes only rise once during the year, and springs 

 of sufficient abundance occur below the works to keep the southern line 

 of canal supplied with water; but in the present case, the destruction 

 of these bunds or dams, and the loss of the head supply from the moun- 

 tain streams, would leave the canal nearly dry, as there are but a few 

 scanty springs in the southern limits. To meet this difficulty the follow- 

 ing form of sluice has been introduced in the dams over the Rogaon 

 and the Muskara rivers, on the Doab canal works ; and as the experience 

 of two rainy seasons has proved its efficacy, and shewn a facility of 

 working, which was in a measure unexpected, I cannot do better than 

 enter into a short description, accompanying it by a sketch, which will 

 also exhibit the high-water mark of the floods that have occurred within 

 the last two seasons. 



Fig. 1 — Represents a tranverse section through the centre opening of the Mus- 

 kara dam. The gate being closed, the flank revetment is shewn at the back. 

 The horizontal lines explain the different levels at which the canal supply may 

 be regulated. The two upper lines shew the high-water marks of floods in the 

 Tains of 1830 and 1831. The former of 8 feet 9 inches, and the latter of 19 

 feet, from the flooring of the dam. 



Fig. 2— Shews an elevation of three openings of the dam, with the sluice gates 

 at different angles, the windlasses and chains fixed, &c. 



Fig. 3— Shews three similar openings, with the gates dropped, and the windlasses, 

 chains, &c. removed, as happens in the height of the rains, when the rivers are 

 subjected to continual floods. The gates moreover act as self- regulators on certain 

 occasions, especially on the approach of the flood water from the hills, which is 

 generally sudden, although its approach is perfectly well known to the inhabitants 

 of this part of the country. 



The gates are made to fit the grooves in the masonry as closely as possible, so as 

 not to fall by their own weight, but to depend on the increased pressure of the rise 

 of water for their removal in these sudden floods : the arrangement on these occa- 

 •ionsis simple, the catches fixed to the bit-heads are removed from the ratchet wheels 



